drm/amd/display: Fix divide by zero in calc_psr_num_static_frames

calc_psr_num_static_frames() divides by vsync_rate_hz before checking
whether it is zero:

	frame_time_microsec = 1000000 / vsync_rate_hz;

This can trigger a divide-by-zero bug if an invalid refresh rate is
passed in.

Rewrite the calculation to directly compute the number of frames needed
for at least 30 ms using DIV_ROUND_UP(). This avoids the invalid divisor
and removes the temporary frame_time_microsec calculation.

Keep the existing fallback behavior of 2 static frames when
vsync_rate_hz is zero.

Fixes: 4cef2ac4c795 ("drm/amd/display: Introduce power module on Linux")
Reported-by: Dan Carpenter <error27@gmail.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Ray Wu <ray.wu@amd.com>
Cc: Chenyu Chen <chen-yu.chen@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

0 files changed, 0 insertions, 0 deletions